1. Field of the Invention
The present invention relates to a method of and an apparatus for generating tint pattern data used for producing tint patterns by means of which a color print is reproduced.
2. Description of the Prior Art
In a color printing process, there are some cases where tint patterns producing respective uniform colors are printed on the same printing paper to produce a color print on which respective tint patterns are printed in contact with each other but without a blank line between them.
The following steps are generally carried out in order to produce such tint patterns. First, a line drawing is manually prepared by a designer, which line drawing defines outlines of different pattern areas to which respective uniform colors are assigned. A block copy of the line drawing is made and a positive picture of the block copy is taken as an original to be set for a process scanner. The process scanner reads the original picture to produce image data expressing the line drawing. An operater determines the respective uniform colors for the different pattern areas in the drawing by inputting color-assigning data into the process scanner. The process scanner generates tint pattern data expressing the colors in respective pattern areas of the line drawing and produces halftone positives or halftone negatives of the tint patterns as a function of the tint pattern data.
However, if the tint pattern data are generated so as to express the colors only at the inside of the outlines, the printed matter to be produced on the basis of the tint pattern data includes blank lines, that is, white lines on which no ink is printed in place of the outlines.
In order to prevent the occurrence of blank lines, the tint patterns may be expanded to cover the areas on which the outlines are positioned. However, it is not easy in general to expand the tint patterns by modifying the tint pattern data in the process scanner as well as modifying the tint patterns manually because respective widths of the outlines are not constant in the line drawing. In other words, when the tint pattern data are modified to expand the tint patterns by a constant width all around under the condition that the constant widths is smaller than the largest width of the outlines, some blank lines appear at some areas on the printed matter where parts of the outlines of larger width than the constant width are positioned. On the other hand, if the constant width is larger than the smallest width of the outlines, two different color inks of the neighboring pattern areas are overlapped on those areas where parts of the outlines of smaller width than the constant width are positioned.